1. Field of the Invention
This invention is in the field of torque governing and speed governing of engines and particularly for engines whose torque and power varies appreciably over a period of several cycles or revolutions.
2. Description of the Prior Art
Engines developing mechanical torque and power may experience periodic torque and power variations when operated in various ways. Torque variations can be of two types, in-cycle torque variations and periodic torque variations as defined hereinafter. When torque variation occurs during the time of an engine cycle, this variation is herein and in the claims defined as an in-cycle torque variation. A cycle of an engine occurs within the time interval, expressed usually in engine output shaft revolutions, for completion of at least one single cycle of that kind of engine. For example, for a four-stroke cycle gasoline or diesel engine, two revolutions of the engine crankshaft are needed to complete at least one single engine cycle. For turbine engines, a single shaft revolution completes at least a single cycle in that each moving blade is then returned to its original starting point to recommence passing the fixed nozzles. When torque variation occurs at corresponding times or positions between separate engine cycles, this variation is herein and in the claims defined as a periodic torque variation and is a longer term variation of torque than is an in-cycle torque variation. When an engine is running at essentially steady speed, periodic torque variations create corresponding power output variations.
Where a reasonably steady torque is desired to be delivered from the final power output shaft, it is common practice in prior art of engines to add a flywheel to the engine in order to reduce in-cycle torque variations in the final power output shaft. When torque developed by the engine exceeds delivered torque, the flywheel speeds up and the excess power is transformed into flywheel kinetic energy. When torque developed by the engine is less than delivered torque, the flywheel slows down and some of its kinetic energy is delivered into the final power output shaft. In this way, a flywheel can act to reduce torque variations in the final power output shaft of an engine by use of a small speed variation.
In theory, a flywheel can also be used similarly to reduce torque variations of the periodic type, but this is usually impractical since these longer term periodic torque variations would require use of either an excessively large and heavy flywheel, or of an excessive speed variation in the final power output shaft, or of an excessively high operating speed of the flywheel.
Examples of engines experiencing periodic torque and power variations are as follows:
a. The engine utilized in my cross-referenced U.S. Patent application entitled, "Improved Cyclic Char Gasifier." PA1 b. The engine utilized for driving the compressor in U.S. Pat. No. 2,675,672, C. Shorner. PA1 c. A wind-driven engine. PA1 d. A water turbine utilizing tidal lift and rise as its energy source. PA1 e. A steam turbine, driving an electric generator, whose exhaust steam is used for building heating purposes and whose steam flow rate is set by this heating load. PA1 f. An internal combustion engine or a gas turbine engine whose fuel supply rate may vary with time as, for example, for a sewage treatment plant whose evolved gas is the engine fuel. PA1 a. The intake mixture throttle on a gasoline engine. PA1 b. The fuel flow rate control on the injection pump of a diesel engine. PA1 c. The inlet steam pressure throttling valve on a steam turbine. PA1 d. The inlet steam nozzle flow area controller on a steam turbine. PA1 e. The fuel flow rate control for a gas turbine engine. PA1 f. The inlet nozzle flow area controller on a gas turbine or a water turbine. PA1 A. "Elements of Mechanism," P. Schwamb, A. Merrill, W. James, John Wiley, 1930; Chap. 8, page 198 figure 240, page 192 figure 232. PA1 B. "Vibration Problems In Engineering," S. Timoshenko, 2nd Ed., D. Van Nostrand, 1937; page 453 to 456. PA1 C. "Mechanical Engineering Experimentation," G. Tuve, McGraw-Hill, 1961; Chap. 4 pages 83 to 85, chap. 5 page 127. PA1 D. "Mechanical Engineering Experimentation," G. Tuve, McGraw-Hill, 1961; chap. 4 pages 71 to 72. PA1 E. "Mechanical Engineering Experimentation," G. Tuve, McGraw-Hill, 1961; chap. 4 pages 76 to 77.
In some applications these periodic torque and power variations are unimportant as, for example, when a wind-driven engine is used to pump water into a tank. In other applications, these periodic torque and power variations create serious control problems as, for example, when a large steam turbine or gas turbine engine is generating fixed frequency electric power for delivery into a regional electric power grid. In this latter example, the power input variations due to the varying engine must be compensated by offsetting power variations of other engines seving the same power grid by action of the governors on the offsetting engines. These required governor control actions on the offsetting engines may significantly reduce their efficiency.
Practically all engines are equipped with a means for regulating the engine torque output and examples of these torque regulator means are as follows:
Frequently only one of these torque regulator means is used alone, but in some applications combination of two or more torque regulator means are used. For example, in some large steam turbines, torque is regulated by inlet steam throttling valves for small changes and also by nozzle flow area controllers for large changes.
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